The present invention relates to a virtual vehicle transmission test cell including an input motor, an output motor, environmental controls, and a transmission cooler for cycling a transmission through predetermined test schedules without installing the transmission in a vehicle to perform the testing.
Traditionally, automotive transmissions have been tested in a transient state by installing the transmissions in test vehicles or by attaching the transmissions to test engines. Such conventional testing has provided various challenges.
For instance, in order to use an internal combustion engine for testing, various engine accessories, such as a fuel supply system, an exhaust system, an ignition system, and so forth, are required. Furthermore, the clean testing environment requires a ventilation system and noise proof facility. Accordingly, facility costs become significant when using an internal combustion engine for testing transmissions.
Also, the performance of the internal combustion engine tends to be influenced by environmental conditions, such as atmospheric temperature, pressure, etc. These conditions are difficult to simulate, therefore the test results may be unreliable.
Further, since the test is performed by utilizing the engine which is to be used with the transmission, the transmission test cannot be performed unless the engine is provided. Accordingly, when a new engine and transmission are to be developed, testing of the transmission cannot be performed until after the engine design is completed and the engine is built. Therefore, development of the transmission is delayed in relation to timing of the engine design and build.
To date, no transmission test device has been able to use an electric motor to simulate the engine in the transient test condition because electric motors typically have a much higher angular mass moment of inertia than that of an engine. The inertia increases with increasing horsepower. Accordingly, a transmission attached to such a motor with a high moment of inertia would likely be destroyed in a transient test.
The present invention provides a virtual vehicle transmission test cell in which a low inertia input motor is used to simulate vehicle engine torque, speed and inertia; an output motor is used to simulate the load that a transmission experiences in a vehicle; and an environmental simulation provides control of ambient conditions and transmission cooling.
The virtual vehicle transmission test cell is a test facility that tests the transmission while simulating other vehicle interfaces. These interfaces are transmission control, engine power, driveline, gross vehicle weight, vehicle acceleration, aerodynamic drag, rolling resistance, road courses, transmission mounting attitude and transmission thermal environment and vehicle heat rejection. This test cell enables transmission development to move from the road to the lab while incorporating math modeling for the interfaces.
The virtual vehicle transmission test cell combines several technologies not previously integrated in a test facility. The first key technology is a low inertia, high response AC motor and drive. This motor has performance to simulate engine inertia, which includes the ability to make the apparent inertia of the motor more or less than the motor such that it can simulate the torque of a fuel firing engine. The motor has the capability to simulate a high fidelity torque trace driven by firing pulses of the fuel firing motor. The input motor simulates engine speed and torque during transmission shifting, and is capable of handling thrust loads generated by the transmission. The motor is also tiltable so that different transmission installation angles can be tested.
A transmission controller is used to run transmission control algorithms. Alternatively, a production controller may be used and tested along with the transmission. The thermal environment the transmission experiences in a vehicle is simulated by an environmental controller. A transmission cooler is also provided to control oil temperature of the transmission. This laboratory transmission cooler simulates a variety of cooling systems from a range of vehicles. An output motor simulates vehicle imposed loads so that the output system responds like the desired vehicle driveline. The output motor simulates vehicle load conditions using mathematical road course data so that the transmission experiences a close approximation of in-vehicle output loads.
The virtual vehicle transmission test cell allows transmissions to be developed when the corresponding engines and/or vehicles do not yet exist.
According to one aspect of the invention, a system for testing an automotive transmission according to a predetermined test schedule which avoids having to install and drive the transmission in a vehicle to perform the testing is provided. The system includes an input motor operatively connectable to an input of the transmission for providing rotational drive thereto in simulation of the predetermined test schedule. An output motor is operatively connectable to an output of the transmission for providing rotational resistance thereto in simulation of the predetermined test schedule. An environmental chamber substantially encloses the transmission, and an environmental controller controls the ambient conditions within the environmental chamber. A transmission cooler is provided for controlling the rejection of heat from the transmission. The predetermined test schedule includes gear shifting of the transmission between a plurality of forward speed ratios, and at least one reverse speed ratio.
The system may also include an apparatus for adjusting angular articulation of the transmission. Further, an input motor controller is provided for controlling rotational drive of the input motor to selectively simulate the speed, acceleration, torque, inertia and/or other performance aspects of an engine according to selected speed, throttle position, torque mapping and/or other parameters. An output controller is provided for selectively controlling the rotational resistance of the output motor to selectively simulate the speed, deceleration, torque, inertia and/or other performance aspects of an after-transmission drive train of a selected vehicle according to selected vehicle aerodynamics, vehicle mass, road conditions, air/weather conditions, load carrying, torque mapping and/or other parameters. The after-transmission drive train includes one or more of a drive shaft, a differential unit, a power take off unit, and a set of wheels.
A plurality of speed, torque, temperature, pressure, position, flow rate, humidity, and/or other sensors are operatively arranged to detect various speeds, torques, temperatures, pressures, positions, flow rates, humidities, and/or the like at selected points in the system.
The transmission cooler includes means for selectively controlling the temperature differential between a supply of transmission fluid to the transmission and a return of transmission fluid from the transmission and/or means for selectively controlling the flow rate of at least the supply of transmission fluid to the transmission. The first heat exchanger is connected to the supply and return of transmission fluid, and can be situated inside or outside of the environmental chamber. The means for selectively controlling the restriction (line back pressure) includes a variable orifice valve. A shunt and second heat exchanger may also be provided inside or outside the environmental chamber in communication with the supply and return of transmission fluid to simulate the vehicle or required test conditions.
A ratio-changing gear box may be operably connected to the output motor and operably connectable to the output of the transmission.
A transmission controller may be provided for selectively controlling the gear shifting of the transmission in response to virtual vehicle speed and virtual throttle position according to the predetermined shift schedule.
A test automation system controller (TAS) may be operatively connected with the input motor controller, the output motor controller, the environmental controller and the transmission cooler for controlling testing of the transmission. Further, all components of the virtual test cell may be controlled by the test automation system.
An input torque meter may be operatively connected to the input motor and an output torque meter may be operatively connected to the output motor and the output motor controller.
The apparatus for adjusting angular articulation may comprise a platform supported by a plurality of hydraulically adjustable supports to provide six degrees of freedom in attitude adjustment.
Preferably, the input motor is a 330 kW, 9000 rpm AC motor with an inertia simulation capability between approximately 0.05 and 0.25 kgm2, or preferably approximately 0.12 kgm2 to simulate the inertia of a V8 engine. The dynamometer (i.e., the motor and motor controller) includes a PWM converter with a closed loop flux vector voltage inverter.
According to another aspect of the invention, a method is provided for virtual vehicle testing of an automotive transmission according to a predetermined test schedule which avoids having to install and drive the transmission in a vehicle to perform the testing. The method includes the steps of:
a. providing a virtual vehicle test system as described above;
b. installing a transmission into the virtual vehicle test system, such that the input and output of the transmission are operatively connected to the input motor and output motor, respectively;
c. operating the input motor through means for selectively controlling the rotational drive thereof to simulate a selected engine according to the predetermined test schedule, and operating the output motor through means for selectively controlling the rotational resistance thereof to simulate a selected vehicle and selected vehicle affecting conditions according to the predetermined test schedule;
d. permitting the transmission to shift among its various gears according to the predetermined shift schedule in response to the virtual vehicle speed and virtual throttle position; and
e. evaluating the performance of the transmission in its execution of the shifting of step d according to preselected performance criteria.
The method may further comprise modifying the transmission and/or the predetermined shift schedule, and repeating steps c, d and e.
According to a further aspect of the invention, a process is provided for optimally matching the candidate vehicle and engine designs with candidate transmission designs which avoids having to install and drive a corresponding physical transmission in a corresponding physical vehicle having a corresponding physical engine. The process includes the steps of:
a. selecting a candidate vehicle design and a candidate engine design;
b. obtaining respective performance characteristics for the candidate vehicle and engine designs according to at least one base line test schedule;
c. selecting a candidate transmission design;
d. selecting a shift schedule for the candidate transmission design;
e. providing a physical transmission corresponding to the candidate transmission design;
f. testing the physical transmission in the virtual vehicle test system as described above;
g. evaluating the performance of the physical transmission according to preselected performance criteria;
h. executing at least one step selected from a group comprising:
i. modifying the physical transmission,
ii. selecting an alternate candidate vehicle design and obtaining performance characteristics therefor according to the previously selected at least one test schedule,
iii. selecting an alternate candidate engine design and obtaining performance characteristics therefor according to the previously selected at least one test schedule,
iv. obtaining new performance characteristics for the candidate vehicle and/or engine design according to an alternate test schedule,
v. selecting an alternate candidate transmission design and providing an alternate physical transmission corresponding thereto, and
vi. selecting an alternate shift schedule;
i. Repeating at least steps f and g.
Further, steps f through i above may be repeated as needed until the performance of the physical transmission substantially meets the preselected performance criteria.
The virtual vehicle transmission test cell may also be used to test the performance of a transmission controller to be used with the transmission.
Accordingly, benefits to be realized by using the invention include removing the transmission from the critical development path of vehicle programs; improving the development environment; reducing costs by elimination of fuel and fuel handling in exhaust facilities of the laboratory; enhancing capability to test engines and vehicles that do not yet exist; reducing cost of the development process due to more controlled testing and removal of vehicles from road testing; and providing potential to perform validation and calibration in a test cell instead of on the road.
The above objects, features, advantages and other objects, features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.